SMS has several advantages. It is more discreet than a phone conversation, making it the ideal form for communicating when you don't want to be overheard. It is often less time-consuming to send a text message than to make a phone call or send an e-mail. SMS doesn't require you to be at your computer like e-mail and instant messaging (IM) do -- although some phones are equipped for mobile e-mail and IM services. SMS is also a convenient way for deaf and hearing-impaired people to communicate.
SMS is a store-and-forward service, meaning that when you send a text message to a friend, the message does not go directly to your friend's cell phone. The advantage of this method is that your friend's cell phone doesn't have to be active or in range for you to send a message. The message is stored in the SMSC (for days if necessary) until your friend turns his cell phone on or moves into range, at which point the message is delivered. The message will remain stored on your friend's SIM card until he deletes it.